1. Field of the Invention
This invention relates to an improved process for disrupting cells, and in particular to a process for disrupting cells of a polysaccharide-producing microorganism of the genus Pseudomonas.
2. Description of the Prior Art
In microbiological processes it is often necessary in the later stages to disrupt the bacterial cells. Especially in the microbial production of polysaccharides for use as viscosifiers in enhanced oil recovery this is a major requirement. Cellular debris and non-viable bacteria have to be removed from the polysaccharide-containing solution before these solutions can be used in enhanced oil recovery operations, because it is the presence of these particulate solids in the polysaccharide solution which can present considerable difficulty in field application of the polymer flood when causing plugging of the rock face and injection water filters.
In European Patent Application No. 0078556, a process for cell disruption is described which comprises the contacting of an aqueous, cell-containing medium containing microorganisms, e.g. of the genus Pseudomonas, known to produce polysaccharides, with a protease enzyme, wherein the enzymic contact is preceded by contact with a surfactant.
Further research efforts on cell disruption have now resulted in the surprising finding that a remarkable improvement, especially in the efficiency of the surfactant treatment step, is achieved when the cells of microorganisms of the genus Pseudomonas contain one or more RP4 and/or RP4::Mu.sub.ts plasmids. For a description of these plasmids, reference is made to Datta, N. et al., Journal of Bacteriology, Vol. 108, pp 1244-1249 (1971), and Boucher, C., et al., Journal of General Microbiology, Vol. 98, pp 253-263. Although Pseudomonas cells comprising one or more of these plasmids appear to be more easily lysed by the surfactant than Pseudomonas cells not containing these plasmids, derivatives of other biopolymer-producing bacteria containing these plasmids showed no change in their sensitivity to the surfactant.
It might be possible that plasmid/transposon mutagenesis occurs in the Pseudomonas-DNA, which means that pieces of DNA from the plasmids integrate in Pseudomonas-DNA and in this way activate or inactivate certain genes which are responsible for rendering the Pseudomonas cells more sensitive to the surfactant.
Therefore, in this application the description "Pseudomonas cells containing one or more RP4 and/or RP4::Mu.sub.ts plasmids" not only encompasses Pseudomonas cells containing plasmids without the occurrence of transposon mutagenesis but also Pseudomonas cells in which plasmid transposon mutagenesis occurs or has occurred.